1. Field of the Invention
The present invention relates to a belt inspecting apparatus for inspecting the surface state of a belt.
2. Description of the Related Art
Continuously variable transmissions (CVTs) for use in automobiles employ a metal belt assembly as a means for transmitting drive power from the engine to the drive shaft. The metal belt assembly includes a stack of thin metal belts assembled together. The metal belt assembly is required to be flawless in order to smoothly transmit the drive power to the drive shaft without fail.
There has been proposed a belt inspecting apparatus for automatically inspecting a metal belt for flaws (see Japanese Laid-Open Patent Publication No. 2004-077425).
FIGS. 24A through 24C of the accompanying drawings show transverse cross-sectional shapes of thin metal belts. FIG. 24A illustrates a normal profile 200, as indicated by the solid line, representing an appropriate cross-sectional shape of the thin metal belt. FIG. 24B illustrates, in addition to the normal profile 200 indicated by the dotted line, an abnormal profile 202, as indicated by the solid line, representing an inappropriate cross-sectional shape of a thin metal belt, which has an abrasion flaw on a side surface thereof. FIG. 24C illustrates, in addition to the normal profile 200 indicated by the dotted line, an abnormal profile 204, as indicated by the solid line, representing an inappropriate cross-sectional shape of a thin metal belt, which has an impression flaw on a side surface thereof. The belt inspecting apparatus disclosed in Japanese Laid-Open Patent Publication No. 2004-077425 determines deviations of the abnormal profiles 202, 204, shown in FIGS. 24B and 24C, from the normal profile 200 shown in FIG. 24A, and automatically determines whether the metal belts are acceptable or not based on such determined deviations.
When a metal belt is manufactured, dust particles tend to be applied to the metal belt. Although the applied dust particles do not make the metal belt unacceptable as a product, in the above belt inspecting apparatus, it is difficult to distinguish such dust particles from actual flaws on the metal belt. The apparatus therefore is liable to judge the dust particles as producing the abnormal profiles 202 or 204.
In particular, the metal belt comprises a flat portion, and curved portions, which are continuous to opposite edges of the flat portion. The belt inspecting apparatus is more likely to ignore flaws on the curved portions than flaws on the flat portion. In addition, the belt inspecting apparatus is unable to clearly sort out dents from bumps on the metal belts, and hence the apparatus is unable to separate dust particles from actual flaws that are as large as the dust particles.